FAQs: Fastwarm® Thermal Insulation Boards

• What are Fastwarm® Thermal Insulation boards?
• What are Fastwarm®-Xtra Tile Backer boards?
• Why not use tile backer/construction boards instead of Fastwarm® thermal insulation?
• When should I consider using a tile backer board?
• What type of underfloor heating insulation will give me the best all round performance?
• How will Fastwarm® floor insulation improve the performance?
• I only have room for a shallow screed, can I use Fastwarm floor insulation boards?
• What depth of floor insulation do I need for underfloor heating?
• How do I fix Fastwarm® insulation & Fastwarm®-Xtra tile backer boards to the sub-floor?
• Is there any special adhesive I need to use to tile over Fastwarm boards?
• If I use Fastwarm insulation how quickly can I expect my heated tile floor to get warm?
• Can I tile straight on top of Fastwarm® boards?
• Can I use Fastwarm® boards to adjust the height of my floor?
• Can Use Fastwarm®-Xtra tile backer insulation boards to stiffen a wooden sub-floor prior to tiling?
• Do I need thermal insulation with a reflective surface?
• Isn't thermal floor insulation expensive?

What are Fastwarm® thermal insulation boards?

Fastwarm® thermal insulation boards are manufactured from extruded polystyrene foam, produced without the use of CFC or HCFC blowing agents, have zero ODP and are fully recyclable. Designed to meet the very specific needs of the under-floor heating industry: extremely thermally efficient and ultra strong, suitable for electric heating cable installations or water underfloor heating systems: Fastwarm insulation boards are available in various depths from 6mm to 80mm.

Fastwarm® thermal insulation boards should only be used over solid cement screed or concrete sub-floors.

What are Fastwarm®-Xtra tile backer boards?

Fastwarm®-Xtra Tile Backer boards (also known as construction boards) consist of an inner core of extruded polystyrene covered with a reinforced glass fibre mesh, coated with a polymer-cement outer face to give them extra rigidity. This additional rigidity provides tensile strength, allowing the tile backer board to be used as a wallboard to tile on.

Fastwarm®-Xtra tile backer boards are also suitable for prepared wooden sub-floors that have previously been strenthened and well screwed down.

The construction of Fastwarm®-Xtra tile-backer boards are totally waterproof and rot-resistant, making them especially suited for areas of high moisture content like wet-rooms and bathrooms.

The extruded polystyrene core provides exceptional thermal properties, making Fastwarm®-Xtra tile backer boards the ideally solution for underfloor heating, reducing wasted heat loss into the sub-floor.

Why not use tile backer/construction boards instead of Fastwarm® thermal insulation?

When used as floor insulation for underfloor heating applications over a cement screed or concrete sub-floor, this strengthened outer cement polymer coating is entirely unnecessary: in fact it reduces the overall thermal insulation property of the board - for a typical 10mm tile backer board there is only 8mm of thermal insulation. 

When tile backer boards are used in these type of solid sub-floor applications, the additional rigidity will not add any extra strength (the strength is in the cell structure composition of the inner thermal insulation).

When should I consider using a tile backer board?

Fastwarm®-Xtra tile backer boards should be considered when tiling in wet areas like bathroom walls, showers and wet-rooms, replacing the need to waterproof plaster board. Fastwarm®-Xtra boards are waterproof and rot-resitant, making them the ideal solution to tiled surfaces in areas of high moisture content.

Fastwarm®-Xtra tile backer boards are also suitable for prepared wooden sub-floors that have previously been strenthened and well screwed down.

What type of underfloor heating insulation will give me the best all round performance?

Extruded polystyrene foams will give the best all round performance. Polystyrene has high thermal insulation properties, high compressive strength capable of supporting long-term static loading, waterproof, rot resistant, lightweight, easy to handle, easy to cut and shape with a sharp knife.

Fastwarm® & Fastwarm®-Xtra have identical thermal properties and technical performance and both are suitable for underfloor heating applications.

Fastwarm® thermal insulation boards should only be used for concrete sub-floors.

Fastwarm®-Xtra tile backer boards are suitable for wooden sub-floors.

How will Fastwarm® floor insulation improve the performance?

A high quality thermal barrier will slow the process of heat loss into the sub-floor, significantly improving the performance of an under floor heating system, speeding the initial warm up times and reducing the electricity costs.

I only have room for a shallow screed, can I use Fastwarm floor insulation boards? 

Due to it's inherent strength, Fastwarm® insulation boards can be used in most situations where there is only limited room for the screed.
Fastwarm® thermal insulation boards have approximately double the compressive strength characteristics of standard building insulation boards.

What depth of floor insulation do I need for underfloor heating?

A simple rule of thumb is to incorporate as much thermal insulation wherever possible below the underfloor heating system: the principals are the same for water as well as electric installations. For new build projects the insulation depth is easy to plan but in a typical refurbish situation for existing sub-floors, this is not always possible, especially where the overall finished floor height may restrict the depth available to add the thermal insulation. However, even a 6mm thermal layer directly below the underfloor heating will provide a noticeable difference in start-up times, bringing the floor temperature up to an optimum warmth within a much faster time.

Fastwarm® thermal insulation boards are available from 6mm to 80mm.

Fastwarm®-Xtra tile backer insulation boards are only available in 6 and 10mm.

How do I fix Fastwarm® insulation & Fastwarm-Xtra tile backer boards to the sub-floor?

For cement sub-floors, both Fastwarm® & Fastwarm-Xtra insulation boards will readily bond to any good quality rapid setting, water based (solvent-free) floor tile adhesive.

For wooden sub-floors care must be taken to ensure that the floor is firmly fixed to the joists, following the recommended 300mm screwed centres as a guide, prior to applying the flexible floor tile adhesive and bonding the Fastwarm-Xtra tile backer boards - no additional mechanical fixings are required.

Is there any special adhesive I need to use to tile over Fastwarm® boards?

Yes, for cement and wooden sub-floors a rapid-setting flexible tile adhesive will be required. The special polymers added to flexible adhesives will make allowances for any tile floor movements caused through heat expansion and contraction by the underfloor heating: the added polymers will also accommodate any slight flexing in a wooden sub-floor; don't forget, a flexible tile grout will also be required.

If I use Fastwarm® insulation how quickly can I expect my heated tile floor to get warm?

This depends on a number of factors like the sub-floor type and thermal insulation: a cement sub-floor will be slow to warm without a thermal insulation barrier, creating a significant drag on the performance of the under floor heating. A layer of high quality thermal insulation will have a dramatic effect in these circumstances, speeding up the initial warm up times to within 15-20 minutes.

Can I tile straight on top of Fastwarm® boards ?

Where normal foot traffic is anticipated, Fastwarm® insulation boards can be tiled without any special preparation using any good quality flexible floor tile adhesive.

Even without underfloor heating, tiles bonded to Fastwarm® or Fastwarm-Xtra will be warmer as a result, due to the thermal barrier between the tiles and the cold sub-floor.

Can I use Fastwarm®-Xtra tile backer boards to adjust the height of my floor?

Traditional use of plywood is a well-proven method but it is difficult to cut around complicated bathroom objects, is heavy and relatively expensive; it will require fixing to the sub-floor and primed prior to the use of tile adhesive.

Fastwarm®-Xtra tile backer boards will achieve the same result, are easily cut with a sharp knife, available in more manageable sizes, very lightweight, completely waterproof, rot-resistant and relatively low cost.

Can Use Fastwarm®-Xtra tile backer boards to stiffen a wooden sub-floor prior to tiling?

The tile council recommends that a wooden sub-floor should be well screwed down at 300mm centres with a mechanically fixed ply-board layer to stiffen the sub-floor primed in preparation of applying a flexible tile adhesive followed by the tile floor. 

An alternative method is to use Fastwarm®-Xtra tile backer boards over a suitably prepared wooden sub-floor that has been previously strenthened and well screwed down, primed and sealed in the normal way. Fastwarm®-Xtra tile backer boards can be bonded to the stiffened wood sub-floor using a flexible tile adhesive - no additional mechanical fixing is required. After priming and sealing the surface, the underfloor heating can be laid directly on top of the tile backer boards and tiling in the usual way using the same flexible tile adhesive.

Do I need thermal insulation with a reflective surface?

Reflective surfaces will give a greater thermal insulation performance when an air barrier is present (like behind a radiator). If buried within a cement layer then the reflective surface will now act as a conductor and transfer heat or cold. No useful gain can be attributed to a reflective surface when applied in this way.

Isn't thermal floor insulation expensive?

When used in conjuction with an underfloor heating system, an effective thermal barrier should not be seen as a cost but an investment, improving the efficiency of the underfloor heating by reducing the wasted heat energy into the sub-floor. The underfloor heating will be more responsive from a cold start by raising the floor temperature faster as a result of the insulation layer; the overall effect of installing Fastwarm® will be to lower electricty running costs.